Piezoelectric valve and method of manufacturing the piezoelectric valve

ABSTRACT

Provided is a piezoelectric valve in which the valve is opened/closed utilizing a displacement of a laminated piezoelectric element, including: a valve main body having a gas pressure chamber that receives compressed gas supplied externally; and an actuator having a valving element, the laminated piezoelectric element that generates a driving force required for operating the valving element as the displacement, and a displacement enlarging mechanism that enlarges the displacement of the laminated piezoelectric element to be acted on the valving element, the actuator being disposed in the valve main body, in which a surface of the laminated piezoelectric element is coated with silicone in a state in which the laminated piezoelectric element is integrated into the actuator.

TECHNICAL FIELD

The present disclosure relates to a piezoelectric valve in which thevalve is opened/closed utilizing a displacement of a laminatedpiezoelectric element, and a method of manufacturing the piezoelectricvalve.

BACKGROUND ART

A piezoelectric valve is conventionally known in which the valve isopened/closed utilizing a displacement of a laminated piezoelectricelement to eject compressed gas (see Patent Literature 1).

The piezoelectric valve described in Patent Literature 1 utilizesproperties of the laminated piezoelectric element having excellenthigh-speed response performance, and includes a displacement enlargingmechanism that enlarges a small displacement of the laminatedpiezoelectric element based on the principle of leverage.

In the piezoelectric valve, application of a voltage to the laminatedpiezoelectric element causes a displacement of the laminatedpiezoelectric element in an extending direction, the displacement istransmitted to a valving element via the displacement enlargingmechanism, and the valving element is immediately moved to open thevalve.

Moreover, in the piezoelectric valve, cancellation of voltageapplication to the laminated piezoelectric element causes a return forceassociated with return of the laminated piezoelectric element to anoriginal state, the return force is transmitted to the valving elementvia the displacement enlarging mechanism, and the valving element isimmediately brought into contact with a valve seat to close the valve.

The laminated piezoelectric element has excellent features such as lowconsumption energy associated with the operation, suitability forhigh-speed operation, and compactness.

However, the laminated piezoelectric element has a piezoelectric ceramiclayer, and is thus structurally fragile, which may cause broken piecesto be ejected together with compressed gas when the piezoelectric valveis used.

Moreover, the laminated piezoelectric element is vulnerable to ahighly-humid environment. Thus, in a case of using the piezoelectricvalve in a highly-humid environment, moisture may enter the laminatedpiezoelectric element to shorten the life of the piezoelectric valve.

Thus, the inventors of the present invention have proposed coating asurface of the laminated piezoelectric element with a polyolefin-basedresin (see Patent Literature 2).

A piezoelectric valve described in Patent Literature 2 utilizes alaminated piezoelectric element coated with a polyolefin-based resinhaving properties of small Young's modulus and excellent flexibility andhaving properties of small moisture permeability and excellent waterresistance. This prevents broken pieces of the laminated piezoelectricelement from being ejected together with compressed gas when using thepiezoelectric valve. Moreover, even in a case of usage in a highly-humidenvironment, moisture will not enter the laminated piezoelectric elementto shorten the life.

Ejection of broken pieces of the laminated piezoelectric element isprevented by coating the surface of the laminated piezoelectric elementthinly with a polyolefin-based resin. However, in order to preventreduction in insulation resistance of the laminated piezoelectricelement in a high-temperature, highly-humid environment, the surface ofthe laminated piezoelectric element needs to be coated with apolyolefin-based resin thickly to some extent. In that case, themovement of the laminated piezoelectric element may be interfered withto reduce the stroke or to cause a failure to perform a correctoperation.

CITATION LIST Patent Literature

-   [Patent Literature 1] Japanese Patent Laid-Open No. 2013-124695-   [Patent Literature 2] Japanese Patent Laid-Open No. 2016-61412

SUMMARY OF INVENTION Technical Problem

Thus, the present disclosure has an object to provide a piezoelectricvalve that can prevent broken pieces of a laminated piezoelectricelement from being ejected together with compressed gas when in use, canprevent moisture from entering the laminated piezoelectric element toshorten the life even in a case of usage in a highly-humid environment,and can prevent the movement of the laminated piezoelectric element frombeing interfered with to reduce the stroke or to cause a failure toperform a correct operation, and to provide a method of manufacturingthe piezoelectric valve.

Solution to Problem

In order to achieve the above object, the present disclosure is apiezoelectric valve in which the valve is opened/closed utilizing adisplacement of a laminated piezoelectric element, including: a valvemain body having a gas pressure chamber that receives compressed gassupplied externally; and an actuator having a valving element, thelaminated piezoelectric element that generates a driving force requiredfor operating the valving element as the displacement, and adisplacement enlarging mechanism that enlarges the displacement of thelaminated piezoelectric element to be acted on the valving element, theactuator being disposed in the valve main body, in which a surface ofthe laminated piezoelectric element is coated with silicone in a statein which the laminated piezoelectric element is integrated into theactuator.

In the present disclosure, preferably, the surface of the laminatedpiezoelectric element is coated with silicone filled between a pair ofprojecting pieces positioned on both sides of the laminatedpiezoelectric element along a longitudinal direction of the laminatedpiezoelectric element with gaps between the pair of projecting pieces.

In the present disclosure, preferably, the piezoelectric valve furtherincludes a plate disposed in the valve main body, the actuator beingfixed to the plate and disposed in the valve main body together with theplate, in which the pair of projecting pieces are provided on a surfaceof the plate, the pair of projecting pieces being positioned on both thesides of the laminated piezoelectric element along the longitudinaldirection of the laminated piezoelectric element with gaps between thepair of projecting pieces when the actuator is fixed to the plate, andthe surface of the laminated piezoelectric element is coated with thesilicone filled between the pair of projecting pieces in a state inwhich the actuator is fixed to the plate.

Herein, in the present disclosure, silicone means a low-viscositysilicone rubber, and preferably a silicone rubber having a viscosity ofmore than or equal to 0.01 Pa·s and less than or equal to 10.0 Pa·s, andmore preferably, a silicone rubber having a viscosity of 2.5 Pa·s can beused.

Moreover, considering workability, a one-component room temperaturecuring silicone rubber is preferably used. For example, a low-viscositysilicone rubber “KE-3475 (product name)” manufactured by Shin-EtsuChemical Co., Ltd. or the like is preferably used.

In the present disclosure, preferably, the displacement enlargingmechanism is formed of a metallic material, and an interconnection linefor supplying power to the laminated piezoelectric element is molded ina plate formed of a resin material, and an electrode of theinterconnection line exposed from the plate is coated with an insulationmaterial in a state in which the electrode is connected to a lead lineof the laminated piezoelectric element.

In the present disclosure, preferably, the displacement enlargingmechanism is formed of a metallic material, and a lead line of thelaminated piezoelectric element is arranged on an insulating film bondedto a surface of the displacement enlarging mechanism.

Moreover, in order to achieve the above object, the present disclosureis a method of manufacturing a piezoelectric valve in which the valve isopened/closed utilizing a displacement of a laminated piezoelectricelement, the piezoelectric valve including a valve main body having agas pressure chamber that receives compressed gas supplied externally,and an actuator having a valving element, the laminated piezoelectricelement that generates a driving force required for operating thevalving element as the displacement, and a displacement enlargingmechanism that enlarges the displacement of the laminated piezoelectricelement to be acted on the valving element, the actuator being disposedin the valve main body. The method includes supplying silicone onto asurface of the laminated piezoelectric element integrated into theactuator to coat the surface of the laminated piezoelectric element withthe silicone.

In the present disclosure, preferably, the silicone is supplied onto thesurface of the laminated piezoelectric element integrated into theactuator to coat the surface of the laminated piezoelectric element withthe silicone filled between a pair of projecting pieces positioned onboth sides of the laminated piezoelectric element along a longitudinaldirection of the laminated piezoelectric element with gaps between thepair of projecting pieces.

In the present disclosure, preferably, the piezoelectric valve furtherincludes a plate disposed in the valve main body, the actuator beingfixed to the plate and disposed in the valve main body together with theplate, the pair of projecting pieces are provided on a surface of theplate, the pair of projecting pieces being positioned on both the sidesof the laminated piezoelectric element along the longitudinal directionof the laminated piezoelectric element with gaps between the pair ofprojecting pieces when the actuator is fixed to the plate, and after thelaminated piezoelectric element is integrated into the actuator and theactuator is fixed to the plate, the silicone is supplied onto thesurface of the laminated piezoelectric element to coat the surface ofthe laminated piezoelectric element with the silicone filled between thepair of projecting pieces.

Advantageous Effects of Invention

In the piezoelectric valve of the present disclosure, the surface of thelaminated piezoelectric element is coated with silicone havingproperties excellent in water resistance and water proofness. This canprevent broken pieces of the laminated piezoelectric element from beingejected together with compressed gas when in use, and can preventmoisture from entering the laminated piezoelectric element to shortenthe life even in a case of usage in a highly-humid environment.

Moreover, in the piezoelectric valve of the present disclosure, thesurface of the laminated piezoelectric element is coated with siliconehaving properties whose elasticity and compressibility are greater thanthose of a conventional polyolefin-based resin. This can prevent themovement of the laminated piezoelectric element from being interferedwith to reduce the stroke or to cause a failure to perform a correctoperation even in a case where the surface of the laminatedpiezoelectric element is coated with silicone thickly to some extent inorder to prevent reduction in insulation resistance of the laminatedpiezoelectric element in a high-temperature, highly-humid environment.

In the piezoelectric valve of the present disclosure, the entirecircumferential surface of the laminated piezoelectric element can beeasily coated with silicone since the surface of the laminatedpiezoelectric element is coated with silicone filled between the pair ofprojecting pieces positioned on both sides of the laminatedpiezoelectric element along the longitudinal direction of the laminatedpiezoelectric element with gaps between the pair of projecting pieces.

In the piezoelectric valve of the present disclosure, the entirecircumferential surface of the laminated piezoelectric element can beeasily coated with silicone since the piezoelectric valve furtherincludes a plate disposed in the valve main body, the actuator beingfixed to the plate and disposed in the valve main body together with theplate, and the pair of projecting pieces are provided on the surface ofthe plate, the pair of projecting pieces being positioned on both thesides of the laminated piezoelectric element along the longitudinaldirection of the laminated piezoelectric element with gaps between thepair of projecting pieces element when the actuator is fixed to theplate, and the surface of the laminated piezoelectric element is coatedwith the silicone filled between the pair of projecting pieces in astate in which the actuator is fixed to the plate.

In the method of manufacturing a piezoelectric valve of the presentdisclosure, silicone is supplied onto the surface of the laminatedpiezoelectric element integrated into the actuator to coat the surfaceof the laminated piezoelectric element with the silicone. This preventsan assembling failure when integrating the laminated piezoelectricelement into the actuator from occurring even in a case where siliconespreads out and adheres to a place other than the surface of thelaminated piezoelectric element.

In the method of manufacturing a piezoelectric valve of the presentdisclosure, the entire circumferential surface of the laminatedpiezoelectric element can be easily coated with silicone since siliconeis supplied onto the surface of the laminated piezoelectric elementintegrated into the actuator to coat the surface of the laminatedpiezoelectric element with the silicone filled between the pair ofprojecting pieces positioned on both the sides of the laminatedpiezoelectric element along the longitudinal direction of the laminatedpiezoelectric element with gaps between the pair of projecting pieces.

In the method of manufacturing a piezoelectric valve of the presentdisclosure, an assembling failure when fixing the actuator into whichthe laminated piezoelectric element has been integrated to the platedoes not occur even in a case where silicone spreads out and adheres toa place other than the surface of the laminated piezoelectric elementsince the piezoelectric valve further includes a plate disposed in thevalve main body, the actuator being fixed to the plate and disposed inthe valve main body together with the plate, the pair of projectingpieces are provided on the surface of the plate, the pair of projectingpieces being positioned on both the sides of the laminated piezoelectricelement along the longitudinal direction of the laminated piezoelectricelement with gaps between the pair of projecting pieces when theactuator is fixed to the plate, and after the laminated piezoelectricelement is integrated into the actuator and the actuator is fixed to theplate, the silicone is supplied onto the surface of the laminatedpiezoelectric element to coat the surface of the laminated piezoelectricelement with the silicone filled between the pair of projecting pieces.

Moreover, in the method of manufacturing a piezoelectric valve of thepresent disclosure, the pair of projecting pieces positioned on both thesides of the laminated piezoelectric element along the longitudinaldirection of the laminated piezoelectric element with gaps between thepair of projecting pieces when the actuator is fixed to the plate areprovided on the surface of the plate. This enables the entirecircumferential surface of the laminated piezoelectric element to beeasily coated with silicone filled between the pair of projectingpieces.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a laminated piezoelectric element.

FIG. 2 is a perspective view of a piezoelectric valve.

FIG. 3 is an assembly exploded view of the piezoelectric valve.

FIG. 4 is an explanatory view of an actuator.

FIG. 5 is an explanatory view in a state in which the actuator is fixedto a valve seat plate.

FIG. 6 is a sectional view of the piezoelectric valve, which is anexplanatory view in a state in which the valve seat plate is disposed ina valve main body.

FIG. 7 is a plan view of an actuator included in a piezoelectric valveaccording to an embodiment of the present disclosure.

FIG. 8 is a plan view in a state in which the actuator is fixed to avalve seat plate included in the piezoelectric valve according to anembodiment of the present disclosure.

FIG. 9 is a cross-sectional view taken along A-A in FIG. 8.

FIG. 10 is a graph showing an ejection pressure property of air ejectedfrom the piezoelectric valve according to an embodiment of the presentdisclosure.

DESCRIPTION OF EMBODIMENT

An embodiment of the present disclosure will be described with referenceto the drawings.

FIG. 1 shows a cross-sectional view of a representative example of alaminated piezoelectric element (hereinafter referred to as a“piezoelectric element”).

A piezoelectric element 1 shown in FIG. 1 has a laminate 4 obtained byalternately laminating piezoelectric ceramic layers 2 and innerelectrode layers 3. The inner electrode layers 3 are exposed at sidesurfaces of the laminate 4. The exploded side surfaces of the respectiveinner electrode layers 3 are coated with an insulation layer 5 in everyother layer. The laminate 4 further has an external electrode 6 thatcovers the insulation layer 5 and conducts with the inner electrodelayers 3 that are not coated with the insulation layer 5.

FIG. 2 shows a perspective view of an example of a piezoelectric valve.FIG. 3 shows an assembly exploded view of the piezoelectric valve inFIG. 2. FIG. 4 shows an explanatory view of an actuator. FIG. 5 shows anexplanatory view in a state in which the actuator is fixed to a valveseat plate. FIG. 6 shows a sectional view of the piezoelectric valve,which is an explanatory view in a state in which the valve seat plate isdisposed in a valve main body.

A piezoelectric valve 10 shown in FIG. 2 to FIG. 6 includes a valve mainbody 20, a valve seat plate 25 disposed in the valve main body 20 andfixed to the valve main body 20, and actuators 30 fixed to both surfacesof the valve seat plate 25 with screws.

The valve main body 20 is a case whose front surface is openable, andincludes therein a gas pressure chamber to be supplied with compressedgas from an external compressed gas supply source (not shown).

Moreover, a connector part 50 is provided on the front surface of thevalve main body 20. A gas inlet 51 for taking in compressed gas into thevalve main body 20 and a gas outlet 52 for discharging compressed gasare open in the front surface of the connector part 50.

An interconnection line substrate 55 for supplying power to thepiezoelectric element 32 is disposed between the valve main body 20 andthe connector part 50. An interconnection line connector 29 forsupplying power to the piezoelectric element 32 via the interconnectionline substrate 55 is disposed on one side end of the connector part 50and at a lateral position of the valve main body 20.

The valve seat plate 25 includes attachment portions for the actuators30 on both of the surfaces, and has a valve seat 26 with which a valvingelement 31 which will be described later of the actuator 30 is to bebrought into contact. Moreover, a lid member 28 for closing the openingof the case is attached to the front surface of the valve seat plate 25.A gas discharge path that communicates from a valve seat plane of thevalve seat 26 to the outlet 52 that is open in the front surface of theconnector part 50 is formed in the lid member 28. Furthermore, a gasinlet path that communicates from the inlet 51 that is open in the frontsurface of the connector part 50 into the valve main body 20 is formedin the lid member 28.

The valve seat plate 25 is molded with a synthetic resin material, forexample, and interconnection lines from the interconnection linesubstrate 55 to the piezoelectric element 32 are molded.

Moreover, electrodes 58 of interconnection lines to be connected to thelead lines 57 of the piezoelectric element 32 as will be described laterusing FIG. 8 are exposed at a rear position of the valve seat plate 25.

The actuator 30 includes the valving element 31 made of rubber,preferably smooth rubber, a piezoelectric element 32 that generates adriving force required for operating the valving element 31 as adisplacement, and a displacement enlarging mechanism 33 that enlargesthe displacement of the piezoelectric element 32 to be acted on thevalving element 31, as shown in FIG. 4.

The piezoelectric element shown in FIG. 1 can be used for thepiezoelectric element 32. Alternatively, a resin-coated piezoelectricelement whose entire circumferential surface including the side surfacesat which the inner electrode layers 3 are exposed is coated thinly withepoxy resin can also be used for the piezoelectric element 32.

The displacement enlarging mechanism 33 has a displacement enlargingsection 34 that enlarges a displacement of the piezoelectric element 32,and a displacement transmitting section 35 that transmits thedisplacement of the piezoelectric element 32 to the displacementenlarging section 34. The displacement enlarging mechanism 33 isarranged symmetrically with respect to an axial line in an operatingdirection of the valving element 31, herein, a straight line(hereinafter referred to as a “center line”) connecting the valvingelement 31 and a longitudinal axial line of the piezoelectric element32.

The displacement transmitting section 35 has a U-shaped base substrate36 to which one end of the piezoelectric element 32 is connected, and acap member 37 to which the other end of the piezoelectric element 32 isconnected. Since the piezoelectric element 32 is disposed in a space ofthe U-shaped base substrate 36, the displacement enlarging mechanism 33has an arrangement symmetric about the longitudinal axial line of thepiezoelectric element 32.

Herein, the piezoelectric element 32 is incorporated into the space ofthe U-shaped base substrate 36 and between the bottom of the U-shapedbase substrate 36 and the cap member 37. By plastically deforming thebottom of the U-shape base substrate 36, the piezoelectric element 32has one end joined to the bottom of the U-shape base substrate 36 andthe other end joined to the cap member 37.

The displacement enlarging section 34 is composed of first and seconddisplacement enlarging sections 34 a, 34 b arranged symmetrically withrespect to the center line.

The first displacement enlarging section 34 a has first and secondhinges 39, 40, a first arm 41, and a first plate spring 42. One end ofthe first hinge 39 is integrated with one side leading end of theU-shaped base substrate 36, and one end of the second hinge 40 isintegrated with the cap member 37. One end of the first plate spring 42is joined to an outer leading end portion of the first arm 41, and oneside end portion of the valving element 31 is joined to the other end ofthe first plate spring 42.

On the other hand, the second displacement enlarging section 34 b hasthird and fourth hinges 43, 44, a second arm 45, and a second platespring 46. One end of the third hinge 43 is integrated with theother-side leading end of the U-shaped base substrate 36, and one end ofthe fourth hinge 44 is integrated with the cap member 37. One end of thesecond plate spring 46 is joined to an outer leading end portion of thesecond arm 45, and the other side end portion of the valving element 31is joined to the other end of the second plate spring 46.

Herein, the displacement enlarging mechanism 33 can be formed integrallyby punching a metallic material such as a stainless material includingan invar material, for example.

In the above-described actuator 30, the piezoelectric element 32 iselongated when applying a current to the piezoelectric element 32 in avalve-closed state. A displacement associated with the elongation of thepiezoelectric element 32 is enlarged in accordance with the principle ofleverage in the displacement enlarging mechanism 33 using the first andthird hinges 39, 43 as a fulcrum, the second and fourth hinges 40, 44 asa point of effort, and the outer leading end portions of the first andsecond arms 41, 45 as a point of load to greatly displace the outerleading end portions of the first and second arms 41, 45.

Then, the displacement of the outer leading end portions of the firstand second arms 41, 45 moves the valving element 31 away from the valveseat 26 via the first and second plate springs 42, 46 to open the gasdischarge path.

On the other hand, when current application to the piezoelectric element32 is stopped in the above-described actuator 30, the piezoelectricelement 32 contracts, and the contraction causes the valving element 31to be seated on the valve seat 26 via the displacement enlargingmechanism 33 to close the gas discharge path.

FIG. 7 shows a plan view of the actuator included in the piezoelectricvalve according to an embodiment of the present disclosure.

In the actuator shown in FIG. 7, the surface of the piezoelectricelement 32, that is, at least the side surfaces of the piezoelectricelement 32 at which the inner electrode layers are exposed are coatedwith a silicone 8 in a state in which the piezoelectric element 32 isintegrated.

In the piezoelectric valve according to an embodiment of the presentdisclosure, for example, a piezoelectric element 32 of the type shown inFIG. 1 whose surface is coated with the silicone 8 can be integrallyincorporated into the actuator 30.

Moreover, in the piezoelectric valve according to an embodiment of thepresent disclosure, the silicone 8 can also be supplied onto the surfaceof the piezoelectric element 32 in the state in which the piezoelectricelement 32 is integrated into the actuator 30 with a dispenser, brush,or the like to coat the surface of the piezoelectric element 32 with thesilicone 8.

The piezoelectric valve according to an embodiment of the presentdisclosure eliminates the concern of an occurrence of assembling failurewhen integrating the piezoelectric element 32 into the actuator 30 evenin a case where the silicone 8 spreads out and adheres to a place otherthan the surface of the piezoelectric element 32 since the silicone 8 issupplied onto the surface of the piezoelectric element 32 in the statein which the piezoelectric element 32 is integrated into the actuator 30to coat the surface of the piezoelectric element 32 with the silicone 8.

The surface of the piezoelectric element 32 is coated with the silicone8 in the state in which the piezoelectric element 32 is integrated intothe actuator 30, and the piezoelectric valve according to an embodimentof the present disclosure can be assembled by fixing the actuator 30 tothe valve seat plate.

Herein, it is sufficient that at least the side surfaces of thepiezoelectric element 32 at which the inner electrode layers are exposedbe coated with the silicone 8, and preferably, it is sufficient that allthe side surfaces (the entire circumferential surface) including theside surfaces at which the inner electrode layers are exposed be coatedwith the silicone 8.

Moreover, in a case of using a resin-coated piezoelectric element whoseentire circumferential surface is coated thinly with epoxy resin for thepiezoelectric element 32, it is preferable to coat the entirecircumferential surface with the silicone 8.

FIG. 8 shows a plan view in a state in which the actuator is fixed tothe valve seat plate included in the piezoelectric valve according to anembodiment of the present disclosure. FIG. 9 shows a cross-sectionalview taken along A-A in FIG. 8.

In the piezoelectric valve according to an embodiment of the presentdisclosure, a pair of projecting pieces 27 are provided at attachmentportions of the actuator 30 on the surface of the valve seat plate 25.The pair of projecting pieces 27 are positioned between thepiezoelectric element 32 and the displacement transmitting section 35and on both sides along the longitudinal direction(elongating/contracting direction) of the piezoelectric element 32 withgaps between the pair of projecting pieces 27 when the actuator 30 isfixed with screws.

Moreover, as shown in FIG. 9, the pair of projecting pieces 27 areformed to be higher than the height of the surface of the piezoelectricelement 32 of the actuator 30 fixed to the valve seat plate 25.

The piezoelectric valve according to an embodiment of the presentdisclosure is the actuator 30 shown in FIG. 7, and the entirecircumferential surface of the piezoelectric element 32 can be coatedwith the silicone 8 filled between the pair of projecting pieces 27 bysupplying the silicone 8 onto the surface of the piezoelectric element32 after fixing the piezoelectric element 32 whose side surfaces atwhich the inner electrode layers are exposed have been coated with thesilicone 8 to the valve seat plate 25.

Moreover, in the piezoelectric valve according to an embodiment of thepresent disclosure, the entire circumferential surface of thepiezoelectric element 32 can also be coated with the silicone 8 filledbetween the pair of projecting pieces 27 by integrating thepiezoelectric element 32 whose surface has not been coated with thesilicone 8 into the actuator 30, fixing the actuator 30 to the valveseat plate 25, and then supplying the silicone 8 onto the surface of thepiezoelectric element 32.

In the piezoelectric valve according to an embodiment of the presentdisclosure, the pair of projecting pieces 27 positioned on both thesides of the piezoelectric element 32 along the longitudinal directionof the piezoelectric element 32 with gaps between the pair of projectingpieces 27 when the actuator 30 is fixed to the valve seat plate 25 areprovided on the surface of the valve seat plate 25. This enables theentire circumferential surface to be easily coated with the silicone 8filled between the pair of projecting pieces 27.

Note that the piezoelectric valve according to an embodiment of thepresent disclosure eliminates the concern of an occurrence of anassembling failure when fixing the actuator 32 to the valve seat plate25 even in a case where the silicone 8 spreads out and adheres to aplace other than the surface of the piezoelectric element 32 byintegrating the piezoelectric element 32 whose surface has not beencoated with the silicone 8 into the actuator 30, fixing the actuator 30to the valve seat plate 25, and then supplying the silicone 8 onto thesurface of the piezoelectric element 32 to coat the entirecircumferential surface of the piezoelectric element 32 with thesilicone 8 filled between the pair of projecting pieces 27.

Herein, in the present disclosure, the silicone 8 indicates alow-viscosity silicone rubber, and preferably a silicone rubber having aviscosity of more than or equal to 0.01 Pa·s and less than or equal to10.0 Pa·s, and more preferably, a silicone rubber having a viscosity of2.5 Pa·s can be used.

Moreover, considering workability, a one-component room temperaturecuring silicone rubber is preferably used, and for example, alow-viscosity silicone rubber “KE-3475 (product name)” manufactured byShin-Etsu Chemical Co., Ltd. or the like is preferably used.

In FIG. 8, the electrodes 58 of interconnection lines molded forsupplying power to the piezoelectric element 32 are exposed at a rearposition of the valve seat plate 25, and are connected to the lead lines57 of the piezoelectric element 32 by soldering. The electrodes 58 ofthe interconnection lines are coated with an insulation material notshown in a state in which the electrodes 58 is connected to the leadlines 57. An insulation resin material such as silicone, for example,can be used as the insulation material.

Moreover, as shown in FIG. 8, the actuator 30 has an insulating film 62bonded at a rear position on the surface of the displacementtransmitting section 35 in the displacement enlarging mechanism 33.

In FIG. 8, the interconnection lines from the interconnection linesubstrate 55 to the piezoelectric element 32 are molded in the valveseat plate 25 to which the actuator 30 is attached. The lead lines 57 ofthe piezoelectric element 32 are arranged on the insulating film 62 soas to be prevented from being in contact with the metallic materialconstituting the displacement enlarging mechanism 33 of the actuator 30.The lead lines 57 of the piezoelectric element 32 are connected, bysoldering, to the electrodes 58 of the interconnection lines exposed atthe rear position of the valve seat plate 25.

Herein, a low moisture-permeable film, for example, can be used as theinsulating film 62.

In the present disclosure, the low moisture-permeable film refers to aresin film made of a material having a moisture permeability of lessthan or equal to 0.5 g/m²·24 hr in 1-mm thickness in an environment at atemperature of 40° C. and a relative humidity of 95%.

A resin film made of a low moisture-permeable material such as, forexample, a polyolefin-based resin film of polyethylene, polypropylene,polyethylene terephthalate, or the like can be used as the lowmoisture-permeable film. Alternatively, a resin film subjected tomoisture permeability reducing treatment such as being coated with amoisture permeability reducing agent such as fluorine can also be usedas the low moisture-permeable film.

The piezoelectric valve according to an embodiment of the presentdisclosure described above is provided with the pair of projectingpieces 27 on the surface of the valve seat plate 25. In a case ofdirectly attaching the actuator 20 to the valve main body 20, a pair ofprojecting pieces can also be provided on an inner wall surface of thevalve main body. In that case, by fixing the actuator to the valve mainbody, and then supplying the silicone 8 onto the surface of thepiezoelectric element, the entire circumferential surface of thepiezoelectric element 32 can be coated with the silicone 8 filledbetween the pair of projecting pieces 27.

In the piezoelectric valve of the present disclosure, the surface of thepiezoelectric element is coated with silicone having propertiesexcellent in water resistance and water proofness. This can preventbroken pieces of the piezoelectric element from being ejected togetherwith compressed gas when in use, and can prevent moisture from enteringthe piezoelectric element to shorten the life even in a case of usage ina highly-humid environment.

Moreover, in the piezoelectric valve of the present disclosure, thesurface of the piezoelectric element is coated with silicone havingproperties whose elasticity and compressibility are greater than thoseof a conventional polyolefin-based resin. This can prevent the movementof the piezoelectric element from being interfered with to reduce thestroke or to cause a failure to perform a correct operation even in acase of coating the surface of the piezoelectric element with siliconethickly to some extent in order to prevent reduction in insulationresistance of the piezoelectric element in a high-temperature,highly-humid environment.

FIG. 10 shows a graph indicating an ejection pressure property of airejected from the piezoelectric valve, which is a graph in which a casewhere the surface of the piezoelectric element is coated with siliconeand a case where the surface of the piezoelectric element is not coatedwith silicone are compared. Note that a coating thickness in the casewhere the surface of the piezoelectric element is coated with siliconeis about 150 μm, and reduction in insulation resistance in ahigh-temperature, highly-humid environment can be prevented.

Experiments were conducted based on the method described in [Example] inJapanese Patent Laid-Open No. 2017-160973. Experimental conditions wereas follows:

(1) Supply pressure of compressed air: 0.15 MPa (a gauge pressure valueat an atmospheric pressure)

(2) Driving voltage: 72V

(3) Set flow rate of compressed air: 39 L/min

(4) Input signal: first pre-pulse time t1=0.098 ms

-   -   First down-time t2=0.08 ms    -   Second pre-pulse time t3=0.6 ms    -   Second down-time t4=0.03 ms    -   Main pulse time t5=0.192 ms

(Energizing time of piezoelectric element: 1 ms)

(5) Detection position of air ejection pressure: 2 mm from leading endof gas discharge path

In FIG. 10, the broken line indicates a result of a piezoelectric valvein which the surface of the piezoelectric element is coated withsilicone. Moreover, the solid line indicates a result of a piezoelectricvalve in which the surface of the piezoelectric element is not coatedwith silicone.

Comparing them, they substantially agree in air ejection pressureproperty, and in the piezoelectric valve according to an embodiment ofthe present disclosure, it was confirmed that the movement of thepiezoelectric element was not interfered with even in a case of coatingthe surface of the piezoelectric element with silicone thickly to someextent in order to prevent reduction in insulation resistance of thepiezoelectric element in a high-temperature, highly-humid environment.

The present disclosure is not limited to the above-described embodiment,and can obviously be modified as appropriate in configuration within therange of the disclosure.

INDUSTRIAL APPLICABILITY

The piezoelectric valve of the present disclosure is extremely usefulsince it is possible to prevent broken pieces of the laminatedpiezoelectric element from being ejected together with compressed gaswhen in use, prevent moisture from entering the laminated piezoelectricelement to shorten the life even in a case of usage in a highly-humidenvironment, and prevent the movement of the laminated piezoelectricelement from being interfered with to reduce the stroke or to cause afailure to perform a correct operation.

REFERENCE SIGNS LIST

-   -   1 laminated piezoelectric element    -   2 ceramic layer    -   3 inner electrode layer    -   4 laminate    -   5 insulation layer    -   6 external electrode    -   7 lead line    -   8 silicone    -   10 piezoelectric valve    -   20 valve main body    -   25 valve seat plate    -   26 valve seat    -   27 projecting piece    -   28 lid member    -   29 interconnection line connector    -   30 actuator    -   31 valving element    -   32 laminated piezoelectric element    -   33 displacement enlarging mechanism    -   34 displacement enlarging section    -   35 displacement transmitting section    -   36 base substrate    -   37 cap member    -   39 first hinge    -   40 second hinge    -   41 first arm    -   42 first plate spring    -   43 third hinge    -   44 fourth hinge    -   45 second arm    -   46 second plate spring    -   50 connector part    -   51 gas inlet    -   52 gas outlet    -   55 interconnection line substrate    -   57 lead line    -   58 electrode    -   62 insulating film

1. A piezoelectric valve in which the valve is opened/closed utilizing adisplacement of a laminated piezoelectric element, comprising: a valvemain body having a gas pressure chamber that receives compressed gassupplied externally; and an actuator having a valving element, thelaminated piezoelectric element that generates a driving force requiredfor operating the valving element as the displacement, and adisplacement enlarging mechanism that enlarges the displacement of thelaminated piezoelectric element to be acted on the valving element, theactuator being disposed in the valve main body, wherein a surface of thelaminated piezoelectric element is coated with silicone in a state inwhich the laminated piezoelectric element is integrated into theactuator.
 2. The piezoelectric valve according to claim 1, wherein thesurface of the laminated piezoelectric element is coated with siliconefilled between a pair of projecting pieces positioned on both sides ofthe laminated piezoelectric element along a longitudinal direction ofthe laminated piezoelectric element with gaps between the pair ofprojecting pieces.
 3. The piezoelectric valve according to claim 2,further comprising a plate disposed in the valve main body, the actuatorbeing fixed to the plate and disposed in the valve main body togetherwith the plate, wherein the pair of projecting pieces are provided on asurface of the plate, the pair of projecting pieces being positioned onboth the sides of the laminated piezoelectric element along thelongitudinal direction of the laminated piezoelectric element with gapsbetween the pair of projecting pieces when the actuator is fixed to theplate, and the surface of the laminated piezoelectric element is coatedwith the silicone filled between the pair of projecting pieces in astate in which the actuator is fixed to the plate.
 4. The piezoelectricvalve according to claim 3, wherein the displacement enlarging mechanismis formed of a metallic material, and an interconnection line forsupplying power to the laminated piezoelectric element is molded in theplate, and an electrode of the interconnection line exposed from theplate is coated with an insulation material in a state in which theelectrode is connected to a lead line of the laminated piezoelectricelement.
 5. The piezoelectric valve according to claim 1, wherein thedisplacement enlarging mechanism is formed of a metallic material, and alead line of the laminated piezoelectric element is arranged on aninsulating film bonded to a surface of the displacement enlargingmechanism.
 6. A method of manufacturing a piezoelectric valve in whichthe valve is opened/closed utilizing a displacement of a laminatedpiezoelectric element, the piezoelectric valve including a valve mainbody having a gas pressure chamber that receives compressed gas suppliedexternally, and an actuator having a valving element, the laminatedpiezoelectric element that generates a driving force required foroperating the valving element as the displacement, and a displacementenlarging mechanism that enlarges the displacement of the laminatedpiezoelectric element to be acted on the valving element, the actuatorbeing disposed in the valve main body, the method comprising: supplyingsilicone onto a surface of the laminated piezoelectric elementintegrated into the actuator to coat the surface of the laminatedpiezoelectric element with the silicone.
 7. The method of manufacturinga piezoelectric valve according to claim 6, wherein the silicone issupplied onto the surface of the laminated piezoelectric elementintegrated into the actuator to coat the surface of the laminatedpiezoelectric element with the silicone filled between a pair ofprojecting pieces positioned on both sides of the laminatedpiezoelectric element along a longitudinal direction of the laminatedpiezoelectric element with gaps between the pair of projecting pieces.8. The method of manufacturing a piezoelectric valve according to claim7, wherein the piezoelectric valve further includes a plate disposed inthe valve main body, the actuator being fixed to the plate and disposedin the valve main body together with the plate, the pair of projectingpieces are provided on a surface of the plate, the pair of projectingpieces being positioned on both the sides of the laminated piezoelectricelement along the longitudinal direction of the laminated piezoelectricelement with gaps between the pair of projecting pieces when theactuator is fixed to the plate, and after the laminated piezoelectricelement is integrated into the actuator and the actuator is fixed to theplate, the silicone is supplied onto the surface of the laminatedpiezoelectric element to coat the surface of the laminated piezoelectricelement with the silicone filled between the pair of projecting pieces.